For forming a gasket from a metal strip by the use of a punch, after punching out a desired profile of a gasket from a metal strip by the use of a single shot type die, a bead forming process is necessary to form a bead in the punch-out part for an increased sealing property.
Conventionally, these processes are independently performed through single shot processes in such a way to punch out a gasket, punch out holes in each gasket and, then, form beads in the gasket. Because of the necessity of at least two independent processes for each gasket, such a bead forming manner is inefficient and is one of cost raising factors.
In recent years, in such circumstances, an improvement has been made to decrease the number of steps by progressively moving a metal strip to a hole punch die and an outer profile punch die arranged side by side, which are conventionally, independently used as single shot dies.
However, even in this manner, although the hole punch die and an outer profile punch die are progressively put in processes, the bead forming must be performed in an independent process.
The present invention has made due to the nature of conditions and has an object to provide a bead forming die for forming beads in a gasket which allows at least three processes of punching holes, forming beads and punching an outer profile of gasket in a progressive process.